Dystonia

What is dystonia?

If dystonia begins in
adult life it tends to be more localised, usually affecting one part of the
body, such as the neck.

Dystonia is a neurological movement disorder, which is characterised by spasms and sustained contractions of the muscles.

These muscle movements are not under voluntary control and they result in repetitive abnormal movements of parts of the body or persistently abnormal postures.

Dystonia can affect virtually any single part of the body or
several different areas at once.

What are the risks?

It's estimated that there are at least 70,000 people in the UK affected with dystonia. It can be very difficult to diagnose and many doctors will never have seen someone with it before. Therefore, the actual number of people with dystonia may be much higher than estimated.

Dystonia affects both men and women. It can affect all age
groups but the most common age of onset is between 40 and 60.

It can also develop in childhood and about 8,000 of the total cases are children, but the pattern is generally different from adult-onset dystonia.

When dystonia starts in childhood it usually begins in the leg
or foot and commonly spreads to involve the entire body. If dystonia begins in
adult life it tends to be more localised, usually affecting one part of the
body, such as the neck or hand.

What are the causes of dystonia?

The causes of dystonia are not fully known, but it is currently thought that the condition results from a malfunction in a part of the brain called the basal ganglia.

The basal ganglia are structures situated deep in the brain.
They help to regulate voluntary and involuntary movement by controlling muscle
contractions in the body.

The problem may mainly lie in an area of the basal ganglia
called the globus pallidus. If this area of the brain is not functioning
correctly then the control of another structure in the brain called the
thalamus is affected.

The thalamus controls the planning and execution of movement
and sends nerves to muscles via the spinal cord. The end result is that muscle
co-ordination is not regulated properly. The wrong muscles will contract on
movement or all muscles will contract unnecessarily causing abnormal movement
and posture.

Muscles positioned around joints usually work in pairs opposite
each other, eg the biceps and triceps muscles of the upper arm bend or
straighten the elbow respectively.

Usually if one muscle of a pair is
contracted the other is relaxed. However, in dystonia both muscles in the pair
contract at the same time leading to the abnormal movement or
posture.

It is thought that in some cases there may be a chemical
imbalance or 'wiring fault' in the basal ganglia. Chemical
transmitters, such as dopamine, convey messages from one nerve cell to another
within the basal ganglia. If this balance is upset then incorrect signals will
be sent out resulting in loss of regulation of co-ordinated movements.

Supporting this theory is the fact that people with dystonia do
not show structural abnormalities of the brain. The 'wiring fault'
theory is therefore more likely because it works at a much smaller scale.

The fault in the basal ganglia may be caused by an inherited factor or be secondary to another problem such as drugs or toxins, or a separate neurological disease. Secondary dystonia is particularly common in children.

How is dystonia classified?

Dystonia can be classified according to the age of onset
(childhood, adolescent or adult) by body distribution (focal, multifocal,
segmental, generalised or hemidystonia) or by the cause (primary, secondary,
'dystonia plus' syndromes or combinations of hereditary and
degenerative causes).

Focal dystonias affect one part of the body such as eyes, neck,
arm or vocal cords and are the most common type.

Multifocal dystonias affect several different unrelated body
parts, such as eyes, hands and vocal cords. Segmental dystonias involve two or
more adjacent body parts, such as the arm and neck.

Hemidystonias affect only one side of the body, and commonly
result from a stroke. Generalised dystonia is more severe and can affect the
entire body.

Primary dystonia refers to the situation where dystonia is the
only sign and there is no identifiable cause or structural abnormality in the
central nervous system.

Secondary dystonia implies there is a clear cause, such as a
change in the structure of the brain, an environmental cause, as part of an
inherited or acquired neurological disease or due to drugs or
toxins.

'Dystonia-plus' syndromes occur when dystonia is
combined with other pathological changes. It includes dopa-responsive dystonia
and myoclonic dystonia.

What are the different types of dystonia?

Focal dystonias

Neck dystonia or cervical dystonia

Neck dystonia or sometimes known as spasmodic torticollis, is the condition of spasm affecting the muscles of the neck, causing the head to assume unnatural postures or turn uncontrollably.

It is the most common of the focal dystonias and affects at least 70,000 people in the UK. The average age of onset is between 30 and 50 and more women are affected than men.

The head may tilt (laterocollis) or twist to one side (rotational torticollis), forward (anterocollis) or backward (retrocollis). The movements may be sustained or jerky (myoclonic torticollis). Muscle spasms or pinching nerves in the neck can be very painful. The neck may eventually be held permanently in one position.

Torticollis usually develops gradually.

At first, the patient may notice that the head turns during everyday activities. In about a quarter of patients the hand may also develop some tremor, especially if trying to correct the involuntary movement.

The tremor is common but not usually disabling and is referred to as an enhanced physiologic tremor. Severity may vary and is individual to the person.

Some sufferers have a history of head or neck injury, but as yet there is no evidence to support the theory that torticollis is directly related to trauma.

Most patients find the condition deteriorates over the first five years, but their symptoms then stabilise.

One third of patients progress to a segmental dystonia, usually involving the arm. The symptoms of about 10 per cent may stop spontaneously, but then later recur.

Patients with torticollis often find that their daily lives are affected. Head turning can prevent a proper view of the road when driving, it may become difficult to eat, brush teeth or apply makeup. Many sufferers find embarrassment and anxiety the major handicap.

No cure currently exists but some treatments such as botulinum toxin injections or sensory techniques such as touching a part of the neck or generally relaxing.

Blepharospasm

Blepharospasm is uncontrollable and often painful muscle contractions around the eye, leading to blinking and closure of the eyelids.

It affects more women than men and in the UK and it is the second most common focal dystonia with approximately 7000 people affected mainly between the ages of 50 to 70.

In very extreme cases, sufferers are unable to prevent their eyes from clamping shut so that despite normal vision they are functionally blind.

Muscles in the face can also become affected causing facial
distortions and grimacing when the patient attempts to open her eyes.

Blepharospasm usually develops gradually.

The first sign a
sufferer may notice is eye irritation and discomfort, light sensitivity and
increased blinking.

They may find that the condition worsens when they are
tired, under stress or reading. Bright flickering lights, smoke or wind can all
irritate the condition making symptoms worse.

It can also be associated with tongue, jaw or mouth dystonia known as Meige's syndrome.

Hemifacial spasm

Hemifacial spasm causes muscles on only one side of the
face to contract.

It affects both men and women and usually develops in middle
age. More than 4000 people in the UK are thought to be affected.

Hemifacial spasm develops gradually. Initially the muscles
surrounding the eye may be affected by muscle spasms, which continue to spread
and affect other muscles on the same side of the face, especially the jaw and
mouth.

Some patients may experience a clicking sound in the ear on the affected
side each time a muscle contracts.

For unknown reasons hemifacial spasm tends to affect the
left side of the face more often than the right.

The cause of hemifacial spasm are not completely understood, but may be related to the irritation of the nerve that controls the muscles of facial expression called the facial nerve.

This may be due to an abnormally placed blood vessel at the back of the brain, near where the facial nerve arises. So hemifacial spasm may not be truly a dystonia.

Oromandibular dystonia

Oromandibular dystonia is where the muscles of the mouth and jaw are affected. It can pull the mouth into unwanted positions and particularly occurs when the person is using their mouth such as eating or talking.

The tongue may be pulled forward, upward, backward or
downward.

Sufferers experience problems eating swallowing or speaking.
Occasionally, this may be drug induced.

Ulceration of the tongue may also occur
due to a continuation of dry mouth and tongue twisting.

Orofacial-buccal dystonia

This dystonia is also known as Meiges or Brueghels syndrome.
It is a combination of blepharospasm and oromandibular dystonia.

Voice dystonia or laryngeal dystonia

Voice dystonia or sometimes called spasmodic dysphonia is a voice disorder caused by involuntary muscles contractions to the vocal muscles.

It's slightly more common in women than in men and normally occurs between 30 and 50.

Sufferers find that their voice sounds strained and strangled, that it takes a lot of effort to speak and that their voice comes out as tremulous, weak or a breathless whisper.

There are two types of spasmodic dysphonia. In the adductor type, speaking causes involuntary excessive muscle contraction of the muscles that bring the vocal cords together.

This causes a strained, strangled, choked voice quality, often with abrupt initiation and termination of voicing, resulting in a broken speech pattern. The patient may sound hoarse, breathless, anxious or groaning.

In the abductor type, there is an overcontraction of the muscles that separate the vocal cords, resulting in a choppy and breathy whispering voice pattern.

Spasmodic dysphonia may follow an infection of the respiratory tract, injury to the larynx or a period of excess voice use.

Most patients find that they are able to use their voices normally in some situations.

Patients with the adductor type may be able to laugh, whisper or sing normally.

Improved speech is noted during emotional or physiological states for example joy, anger or following yawning. Shouting or stress usually makes the condition worse.

Treatment can be difficult and is dependent on the individual. The first line treatment is botulinum toxin injections into the muscles that spasm.

Writer's cramp

In this type of dystonia the muscles of the hand and forearm are affected.

There are 2 types- simple and dystonic.

Simple writer's cramp is caused by over use of the hand, causing muscle strain which can result in grabbing the pen too hard, extension of the fingers and unusual wrist or elbow postures.

The patient complains of tension and discomfort. After a few words the patient is forced to stop and rest. The contraction disappears on stopping writing.

Occasionally it can be dystonic and may occur with a more generalised dystonia and occurs when doing activities other than writing such as holding a knife and fork. Patients often employ trick manoeuvres to overcome the cramp.

Some support their writing hand with their opposite arm, use thick nibbed pens, alter their grip or hold the pen in a closed fist.

Unfortunately the cramp may arise in the other hand.

There are other focal dystonias that are associated with a particular activity or occupation. Examples include typist's cramp, pianist's cramp and golfer's cramp.

Adult-onset primary dystonia

This is a rare subtype of focal dystonia. The symptoms
remain localised to the trunk of the body, but may spread to involve the neck
muscles.

The dystonia does not spread to the leg. Unlike other forms of focal
dystonia it is more common in men than women.

The twisting trunk movements have been likened to the
Leaning Tower of Pisa, and the term Pisa syndrome is occasionally applied to
these dystonias.

'Dystonia-plus' syndromes

Dopamine, (often called 'dopa' which is in fact an intermediate chemical in dopamine's production) is a chemical messenger widely used in the nervous system in passing nerve impulses between nerve cells (neurotransmission).

Dopa-responsive dystonia is rare but treatable form of genetic dystonia, that often responds to levodopa.

Typically it begins in childhood or adolescence and leads to progressive difficulty in walking and in some cases spasticity (limb stiffness). Subtle Parkinson's type symptoms also occur.

The symptoms may fluctuate during the day from relative mobility in the morning to increasingly worse as the day progresses.

This is an important condition to recognise as treatment can result in dramatic improvement in symptoms.

Myoclonic dystonia is a rare type combining dystonia and sudden muscular spasms (myoclonus). The onset is in adolescence or early adult life.

It mainly affects the arms and body. These patients can be very sensitive to treatment with alcohol and a genetic basis has been suggested.

Secondary dystonias

Secondary dystonias are caused by damage or degeneration in the brain.

Causes include head trauma, stroke, a tumour, multiple sclerosis, infections in the brain, injury to the spinal cord, or after chemotherapy, drugs or toxins that affect the basal ganglia, thalamus or brain stem.

Examples of metabolic disorders causing secondary dystonia are Lesch-Nehan syndrome, Niemann-Pick disease and Leigh's disease. All of these causes are rare.

What drugs can cause dystonia?

Certain drugs have been implicated in causing dystonia and this can be in an acute form or more long term known as tardive dystonia. This form of dystonia is referred to as secondary or drug induced dystonia.

Some drugs may not cause dystonia but may aggravate the pre-existing disorder. Patients should avoid these drugs.

The list of drugs causing drug induced dystonic reactions is
long but includes the following.

In general, alcohol does not have an adverse effect on dystonia
but it is rarely seen to hasten it.

Alcohol may also help dystonia,
particularly forms of myoclonic dystonia. People who chronically abuse alcohol
can get a series of involuntary movements or tremors not related to dystonia.
Excess alcohol intake is not advised.

Is dystonia hereditary?

It has long been thought that there is a genetic or hereditary link to dystonia, as relatives of patients suffering from dystonia often also have some kind of tremor or dystonia and this link has now been identified in some types of dystonia.

Thirteen inheritable forms of dystonia have now been identified and are due to genetics.

Childhood dystonia (primary or generalised dystonias) are often inherited through one or more affected/mutated genes.

If a parent has this type of dystonia, there is a 50 per cent chance of passing the gene to their children. The gene is on chromosome 9 and known as DYT1. (This mutation has been observed mainly in Ashkenazi Jews.)

However, even if the child inherits the gene, they may not necessarily develop dystonia. This is known as reduced penetrance.

In the UK about 30 to 40 per cent of people with the affected gene develop dystonia.

Research has shown that the gene DYT1 codes for a newly
recognised protein called Torsin A. Its function is unknown.

However, large
amounts are concentrated in an area of the basal ganglia called the substantia
nigra pars compacta, suggesting it has a role in dopamine neurotransmission.

Late-onset primary torsion dystonia or focal dystonia is
inherited in a more complex manner than the early-onset dystonia. Genes known
as DYT6 on chromosome 8 and DYT7 on chromosome 18 may be involved.

These genes
also have reduced penetrance so only about 12 per cent of people with the
affected gene develop the dystonia.

DYT6 has been found in people whose neck or
head muscles are affected causing problems with neck, speech or facial muscles.
DYT7 has been found in those mainly affected with myoclonic torticollis.

Dopa-responsive dystonia also has a genetic basis. Many patients
have a mutation in a gene known as GCHI (GTP cyclohydroxylase) on chromosome
14.

There's a 50 per cent chance of parents passing on the gene, although with
reduced penetrance. However, it occurs more in women.

Mutations in this gene
cause abnormal production of a chemical called tetrahydrobiopterin, needed to
produce the neurotransmitter dopamine.

The drug levodopa is helpful in treating
this form of dystonia as it increases dopamine levels in the brain.

Myoclonic dystonia also has a genetic component. A mutation in a
receptor for the neurotransmitter dopamine has been found on chromosome 11 or
18.

What can my doctor do?

Your GP can refer you to a neurologist who specialises in
movement disorders. The neurologist may carry out further investigations.

If
you are suffering from blepharospasm, you may be referred to an ophthalmologist
(eye specialist), or if you are suffering from spasmodic dysphonia or
oromandibular dystonia you may be referred to an ear, nose and throat (ENT)
specialist.

How is dystonia diagnosed?

There is no definitive test for dystonia.

Diagnosis depends on
the presence of characteristic clinical symptoms and signs.

The neurologist
will perform a full neurological examination and may also perform
blood tests or a
brain scan to rule
out an illness or injury that may be causing the dystonia.

If no cause can be
found the dystonia is termed 'idiopathic'.

Is there a cure for dystonia?

Currently there is no cure for dystonia. However, there is a
wide range of treatments available.

Although these cannot cure the dystonia
they will improve the symptoms.

What treatment is available?

Finding the right medication may take some time and patience
and trials of several drugs. Not all people respond to the same drug or dosage.

If the effects of one drug wear off the replacement with another drug may help.

Anticholinergics

These drugs inhibit the action, release or production of the neurotransmitter or chemical messenger called acetylcholine, which plays an important part in the nervous system.

They produce a good response in childhood-onset dystonias, more severe dystonias and those with focal dystonias.

Side-effects include dry mouth, blurred vision, constipation, difficulty in urinating, memory impairment or confusion. But your doctor will increase the dosage slowly to reduce the chance of side-effects.

Benzodiazepines

These drugs regulate the neurotransmitter or chemical
messenger GABA (gamma-aminobutyric acid), which helps the brain maintain muscle
control. They have sedative, anti-anxiety and anticonvulsant
properties as well as muscle relaxing properties.

However, they can cause side-effects including another type of abnormal
movements called tardive dyskinesia, possibly with the exception of
tetrabenzine.

Although these drugs have helped some patients others have
reportedly got worse, so they should be used with caution.

Carbamazepine (eg Tegretol) is
an anticonvulsant and antiepileptic. It works in a small number of patients
and may be of use if other treatments have failed.

Cocktail therapy

In some patients, mostly with severe generalised dystonia, a
combination of drugs may be used. This may include benzhexol, baclofen and
tetrabenazine, with or without a benzodiazepine.

Occasionally injection of Baclofen by a pump into the fluid
surrounding the brain and spinal cord (cerebrospinal fluid) may be used for
severe resistant dystonia or aggravated dystonia known as 'dystonic
storm'.

Botulinum toxin

Botulinum toxin injections have been used in the treatment of dystonia since the early 1980s.

Botulinum toxin is produces by the bacterium Clostridium botulinum and is the cause of botulism – an extremely serious form of food poisoning.

In a pure form and tiny doses, it can reduce the muscle contractions and the muscles become weaker. However, the nerve endings grow back after about eight weeks, so the treatment needs to be repeated every two to three months.

Botulinum neurotoxin type A
(Dysport or Botox) is injected into muscles that are painful, tender or
visibly contracting. It is also injected into muscles that contribute to the
abnormal movement.

In very large quantities botulinum can cause fatal paralysis
of the respiratory muscles.

However, in this treatment it's diluted and
injected into specific muscles in very small quantities.

It does not come into
contact with vital organs such as the liver, kidney or heart.

The injections
are slightly uncomfortable and painful for several days. But most people find
that the symptom relief outweighs the pain.

The advantage is that the treatment can be targeted at the muscles causing the problem. There are no permanent or persistent side-effects.

Injections
around the neck may produce difficulty in swallowing termed dysphagia, weakness
of the neck muscles leading to the head dropping forward and rarely, flu-like
illness for a few days.

Treating spasmodic dysphonia with injections into the
vocal cord muscles may cause temporary softness and breathiness of speech or
transient difficulty in swallowing.

Injections around the eye may produce
drooping of the eyelid or weakness of the eye muscles causing double vision or
eye irritation. The side-effects usually disappear in a week or so and are
unpredictable.

This treatment has been shown to significantly improve
dystonia in 75 per cent of patients with spasmodic torticollis.

It is also used
for the treatment of blepharospasm, writer's cramp, and spasmodic
dysphonia, hemifacial spasm and oromandibular dystonia.

The rate of success in
writer's cramp is less than the other focal dystonias with an
improvement in about 60 per cent of patients.

It is not used in tongue
dystonia, as there is an unacceptable rate of adverse affects including
problems with swallowing and speaking.

Resistance to the toxin after repeated treatment is rare but
about 10 per cent of people will develop antibodies to toxin A (BTA-AB), so
treatment becomes ineffective.

In some patients the antibodies drop with time,
whereas in some people they persist for many years. Removal of these antibodies
may be attempted by plasmapheresis (removal of plasma from the blood).

By stopping treatment for 2 to 3 years antibodies may disappear in some patients and the treatment can become effective again.

Botulinum toxin type B, C and F are currently under
development for those patients who develop antibodies or fail to respond to
Type A.

How successful is surgery?

Surgery is reserved for only the most severe cases that do not
respond to medication.

Surgery for dystonia is destructive. The aim is to
interrupt the pathways that maintain the abnormal muscle movements.

It may
involve cutting nerves and muscles or the careful placement of a lesion in the
basal ganglia of the brain to reduce movement.

The operation to damage the area
of the basal ganglia called the globus pallidus is called a pallidotomy.

Pallidotomy can be unilateral or bilateral.

Firstly an MRI scan is performed to study the anatomy of the brain and basal
ganglia. A stereotactic frame, which is a metal jig, is then secured to the
patient's head after giving them a local anaesthetic.

The frame maps out
the areas of the brain for surgery.

Under local anaesthetic, a small hole is
made in the skull and a probe is inserted. The probe is used to make a lesion
in the globus pallidus by applying heat of about 60°C to 80°C. The procedure is
considered to be safe and have minimal adverse affects.

Studies have shown that most patients do experience a marked
improvement in their dystonic movements, although some benefit to a lesser
extent.

Another procedure called deep brain
stimulation has also been developed to treat dystonia.

It's similar
to pallidotomy but reversible as the globus pallidus is stimulated rather than
destroyed. One study found it resulted in a 65 per cent improvement.

Unlike the effect deep brain stimulation has on conditions such as Parkinson's, the effects of the procedure are not instant and typically take several months to produce full effcts. The procedure has been shown to be safe with minimal adverse effects.

Advanced generalised dystonias have been helped, if only
temporarily, by surgical destruction of parts of the thalamus.

The thalamus is
a structure deep in the brain that helps to control movement.

This operation is
called a thalamotomy. It poses a risk of causing speech disturbance as the
thalamus lies near the brain structures that help to control speech.

Other operations that can be performed are ones in which the
nerves directly to the contracting muscles can be severed. Such procedures are
called denervation operations.

Another operation is called microvascular
decompression.

The theory behind this surgery is that arteries may
compress selected nerves and consequently cause dystonic movements.

This is a
common occurrence in hemifacial spasm where the facial nerve that supplies all
the muscles of the face may be compressed by an artery.

In the microvascular
decompression operation a monitoring procedure ensures that all the blood
vessels causing the problem are removed.

Abnormal electrical signals from the
facial nerve are recorded during the operation, when the last blood vessel is
removed the abnormal response disappears.

This intra-operative monitoring
probably explains why the procedure has a greater than 90 per cent success
rate.

Another procedure, which is useful in patients with neck dystonia where botox has failed, is selective denervation. It's an operation in which the nerves supplying the problematic muscles are cut to relieve the symptoms of dystonia.

Other patients with
congenital muscular torticollis have undergone surgical release of contractive
muscle bands or lengthening of the sternocleidomastoid muscle in the neck – the
broad muscle that connects the skull behind the ear with the inner end of the
collar bone.

These operations have been shown to have good long-term benefits.

Other treatment

Physical therapies, such as physiotherapy with ice, heat or
ultrasound, speech therapy for spasmodic dysphonia, acupuncture, osteopathy or
chiropractic techniques help some patients.

However, treatments involving
manipulation of the neck are not recommended for spasmodic torticollis.

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